If you are able to do so, disconnect the batteries. Then finish everything else that needs to be done. Then reconnect the batteries for the end of the quest.
If that doesn't fix it, report the problem to Support.
On your game screen, choose the Settings wheel in the upper corner. Write down your Player ID and then choose the Support button. Scroll all the way down to the bottom of the page until you see a list of categories. (Do not use the white text box in the top half!) Choose a category and then provide your Player ID, and problem details.
If you are using an iOS device, you might not see the category options on the SUPPORT page. If that is the case, you'll need to email them at firstname.lastname@example.org .